1. Field of the Invention
The present invention generally relates the production of tortillas and related products. More particularly, it pertains to an additive composition for corn and other cereal grain flour to impart advantageous qualities to tortillas and related products produced therefrom.
2. Background and Description of Related Art
a. Background
Tortillas
Tortillas, which are prepared from unleavened, unshortened, flat, circular dough pieces generally made from nixtamalized corn or corn flour and baked on a griddle. Corn has been the traditional cereal for the preparation of tortillas and similar food items in Mexico and Central America from masa. However, other cereal grains, such as sorghum or wheat, may be employed for this purpose. The dough which is used in making tortillas and related products generally only contains ground limed or non-limed whole corn and water.
Tortillas may be used to prepare other corn-containing products, such as tortilla chips, corn chips, taco shells, tostadas, enchiladas, burritos, nachos, sopapillas, tamales and other maize and non-maize snacks and products by methods known by those having skill in the art.
Tortillas have a high moisture content (generally about 45 weight percent moisture of the total weight of the tortillas after cooking). This significantly affects their strength, stability and nutrient density.
The strength of the tortillas is directly related to the stability (shelf life) of the tortillas. It is well-known that tortillas, when kept under conditions in which no moisture is lost, nevertheless become hard and inflexible (stale) with the passage of time, and break or crumble easily when flexed or bent. This effect increases with time. Freshly made tortillas are very flexible, but lose their flexibility with the passage of time. The hardening (loss of flexibility) or staling generally increases with decreasing temperature, and are believed to be due to a physico-chemical change in the starch constituent of tortillas (retrogradation). Tortillas, when prepared normally without additives, generally have a maximum shelf life of about 12 to about 15 hours. After such time, they are generally spoiled by microorganisms, and become hard or stale.
For the preparation of refined foods, corn is usually subjected to a milling process. In these processes, the hulls (bran) and germ, which are the structures rich in minerals and vitamins, are more or less completely removed. The refined mill products, such as masa flour, consist chiefly of the endosperm. Portions of the corn kernel removed from the endosperm, such as the hulls or bran, are considered to be waste by-products which are often put into animal feed.
Components of the Maize (Corn) Kernel
Botanically, a maize kernel is known as a caryposis, a dry, one-seeded, nutlike berry in which the fruit coat and seed are fused to form a single grain. Mature kernels are composed of four major parts: pericarp (hull or bran), germ (embryo), endosperm and tip cap. The average composition of whole maize, and its fractions, on a moisture-free (dry) basis is as follows:
Pericarp: The maize kernel is covered by a water-impermeable cuticle. The pericarp (hull or bran) is the mature ovary wall which is beneath the cuticle, and comprises all the outer cell layers down to the seed coat. It is high in non-starch-polysaccharides, such as cellulose and pentosans. (A pentosan is a complex carbohydrate present in many plant tissues, particularly brans, characterized by hydrolysis to give five-carbon-atom monosaccharides (pentoses). It is any member of a group of pentose polysaccharides having the formula (C5H8O4)n found in various foods and plant juices.) Because of its high fiber content, the pericarp is tough.
Germ: The scutellum and the embryonic axis are the two major parts of the germ. The scutellum makes up 90% of the germ, and stores nutrients mobilized during germination. During this transformation, the embryonic axis grows into a seedling. The germ is characterized by its high fatty oil content. It is also rich in crude proteins, sugars, and ash constituents. The scutellum contains oil-rich parenchyma cells which have pitted cell walls. Of the sugars present in the germ, about 67% is glucose.
Endosperm: The endosperm contains the starch, and is lower in protein content than the germ and the bran. It is also low in crude fat and ash constituents.
Tip cap: The tip cap, where the kernel is joined to the cob, is a continuation of the pericarp, and is usually present during shelling. It contains a loose and spongy parenchyma.
Corn Milling
In milling corn to obtain flour, the corn is first cleaned, and is then usually passed through a scourer to remove the tip from the germ end of the kernel. The corn is then tempered by the addition of water to a moisture content which is generally from about 21% to about 24%. The corn is frequently then passed through a corn degerminator, which frees the bran and germ, and breaks the endosperm into two or more pieces. The stock from the degerminator is generally dried to about 14% to 16% moisture in revolving dryers equipped with steam coils, and is then cooled in revolving or gravity-type coolers. The stock is next passed through a hominy separator, which first separates the fine particles, and then grades and polishes the larger fragments into four sizes. The various grades of broken corn are passed through centrifugal-type aspirators to remove any loose bran from the endosperm fragments, and produce milled cereal by-products such as aspirated bran. These by-products are waste products which heretofore had little value.
xe2x80x9cAspirated branxe2x80x9d is an impure form of whole bran which generally contains some of the floury endosperm, and the starch and protein present therein, and some germ, and the protein present therein, and may contain some grits. Generally, most of the germ and grits will already have been removed from the cereal grain at this point in the milling process. It is possible for the aspirated bran to contain no germ, to contain all of the germ, or to contain any amount of germ in between. Similarly, the aspirated bran fraction may contain no grits from the cereal grain, may contain all of the grits, or may contain any amount of the grits in between. The milled cereal by-product or aspirated bran which may be used to prepare the additive composition of the invention should contain at least about 15 weight percent starch, at least about 6 weight percent protein, and at least about 2 weight percent crude fiber. These percentages are based upon the weight of the by-product or bran which naturally includes moisture if it is not subjected to drying. This naturally occurring moisture in the by-product or bran ranges from about 10 to about 15 weight percent of the bran.
Masa Flour and Dough
Masa flour (dry corn flour which has usually been nixtamalized) and masa (corn dough which has usually been nixtamalized) are raw materials which may be used for the preparation of tortillas, corn chips, tortilla chips, taco shells, nachos and similar products.
Nixtamalization is the cooking of cereal grain, such as whole corn kernels, in a medium which usually contains an alkaline agent, such as water containing lime (CaO). Thereafter there is steeping (soaking) of the cereal grain for a period of time, for example, for about three to about fourteen hours, subsequent draining of any remaining cooking liquor, washing of the cereal grains, and grinding of the cereal grains to make with drying a cereal grain flour, which may be added with water to make a cereal grain dough from which tortillas and related products may be prepared. It is well-known that not only tortillas, but also masa dough used to make tortillas, prepared without additives are extremely unstable, and have a relatively short shelf life.
It would be advantageous to provide an additive composition for flour or dough which is used to make tortillas and related products which would significantly increase the strength of the products, and which would increase the shelf life (stability) and staling time of the products from about 12 to about 15 hours to from about 14 to about 21 days. It would also be advantageous to provide such an additive which increases the nutritional value of products produced from the flour or dough by providing such products with a higher fiber content, and with additional vitamins and minerals. Further, it would be advantageous to produce such an additive composition without the production of liquid waste with a material which is essentially a waste by-product from the milling of cereal, such as whole corn. It would also be advantageous to provide tortillas and related products prepared with such an additive which would retain the flavors and other positive attributes of tortillas and related products prepared without such additive.
The additive of the present invention imparts the advantageous properties described above to tortillas and related products. Tortillas and related products prepared with the inexpensive and nutritious additive of is the present invention become stale much more slowly than tortillas and related products produced from flour or dough which do not contain this additive or other shelf life extender. The additive retards hardening with the passage of time, retards loss of flexibility with time, prolongs the shelf life of the tortillas and related products and increases the freshness of both freshly-made tortillas and reheated tortillas and related products.
Moreover, the tortillas and related products produced from such flour or dough will be more nutritious and healthful than products produced from flour or dough which does not contain this additive. They will have a higher fiber content, and also include vitamins and minerals which are present in cereal by-product from which the additive is made.
b. Description of the Related Art
U.S. Pat. No. 3,653,915 does not describe an additive made from a milling by-product, but rather states that mono or diglycerides of long chain fatty acids or polyoxyethylene monostearate may be incorporated into tortilla dough in order to retard the staling of tortillas.
U.S. Pat. No. 3,655,385 does not describe an additive made from a milling by-product, but rather states that a hydrophilic edible gum, such as locust bean gum or gum arabic, may be incorporated into tortilla dough in order to retard the staling of tortillas.
U.S. Pat. No. 4,555,409 states that masa may be prepared from corn and grain sorghum. Processed corn and grain sorghum are blended and ground to form a meal. The patent describes preparing grain sorghum by dehusking the grain, radiating the resulting grain with an infrared source, rolling the grain, cracking the kernels, removing remaining husk, and milling the kernels.
U.S. Pat. No. 4,594,260 describes preparing nixtamalized corn flour by subjecting whole corn kernels to a process of cleaning the kernels, boiling the kernels in an aqueous liquor, crushing the kernels to form a particulate corn material, classifying the particles to produce a hull fraction isolated from the endosperm/germ fraction, subjecting only the hull fraction to a nixtamalization step by heating the hull fraction suspended in an aqueous alkaline solution, draining the spent alkaline liquor, washing the nixtamalized hull fraction, mixing the hull fraction with the untreated endosperm/germ fraction, drying the mixture and grinding the mixture.
Unlike the present invention, the process described in the ""260 patent avoids undue gelatinization of starch contained in the endosperm of whole corn. The corn flour produced by the process contains most of the starch in a hydrated, but not gelatinized, form (columns 9 and 10). Nixtamalization of the endosperm of the kernels is described as not only unnecessary, but undesirable (columns 7-9).
The present invention provides an additive composition which is a by-product of cereal milling wherein the additive enhances the strength and/or shelf life of tortillas and related products made from masa (or other cereal grain) flour or dough. The additive comprises a cereal grain by-product which includes edible starch which has been gelatinized by cooking it with water and an alkaline agent. The starch is present in an amount and is cooked to an extent, such that when the additive composition is added to masa (or other cereal grain) flour or dough at a level, such as at least about 0.5 weight percent, the additive is effective for increasing the strength and/or the shelf life of tortillas or other products made with such flour or dough. The increase in strength or shelf life is relative to tortillas or other products made with masa (or other cereal grain) flour or dough, but without the bran additive composition or any other shelf life extenders. In an important aspect, the additive composition comprises aspirated corn bran having at least about 15 weight percent starch, of which at least about 50 weight percent has been gelatinized, at least about 6 weight percent protein, and at least about 2 weight percent crude fiber. In another important aspect, the starch in the bran is gelatinized by cooking it with at least about 0.05 weight percent, based upon the weight of the bran, calcium oxide or lime or equivalent thereof. This should provide the additive with at least about 0.025 weight percent calcium, based upon the weight of the additive. The additive should also provide a pH of at least about 7 when it is mixed with water and the additive comprises about 10 weight percent of the additive/water mixture.
The invention also provides a masa (or other cereal grain) flour blend and a process for making such flour blend. The flour blend of the invention is mixed with at least about 40 weight percent water to form a dough of the invention. In an important aspect, the additive comprises at least about 0.5 weight percent of masa (or other cereal grain) flour blend, and in a very important aspect comprises from about 1 to about 6 weight percent of the masa (or other cereal grain) flour blend. The masa flour blend is provided by mixing the additive with masa (or other cereal grain) flour.
Tortillas may be prepared from the dough of the invention by known methods. The flavors and other positive attributes of tortillas and related products produced without the additive of the invention are retained when this additive is incorporated into these products.
The invention also includes a process for making the is additive composition. The method comprises mixing aspirated bran comprising at least about 15 weight percent starch with an alkaline agent and water to provide an aqueous alkaline bran mixture and cooking the alkaline bran mixture to gelatinize the starch and provide a cooked alkaline-treated bran. The starch is gelatinized to an extent that when the additive is present in the masa (or other cereal grain) flour at a level of at least about 0.5 weight percent, the additive composition is effective for increasing the strength and/or the shelf life of tortillas as aforesaid. The cooked alkaline-treated bran is dried without first removing aqueous alkaline water, such as lime water, to provide a dried alkaline-treated bran. Thereafter, the alkaline treated bran is milled to a particle size, such that it will pass through a screen mesh with openings of not greater than 0.1 square mm. In an important aspect, the bran is corn bran, the starch is corn starch, and the bran additive composition comprises aspirated bran having at least about 15 weight percent starch, of which at least about 50 weight percent has been gelatinized. In this aspect, the alkaline agent, such as lime, comprises from about 0.05 to about 5 weight percent based upon the weight of the by-product or bran. The amount of lime, water and cooking are effective for gelatinizing the starch.
The process for preparing the additive composition of the present invention does not result in the production of a liquid waste product and, thus, does not result in the production of a potential environmental pollutant.